What is a Digital Multimeter?
- Why are digital multimeters used?
- Types of digital multimeters
- How to choose a digital multimeter
- How to use a digital multimeter
- Digital multimeter resources
A digital multimeter, or DMM, measures and verifies multiple electrical stimuli, including voltage, current and resistance. It’s a daily diagnostic tool used by technicians and electrical engineers and combines the features of a voltmeter, ammeter and ohmmeter. A digital multimeter typically includes probes, clamps or leads, which are inserted into inputs on the instrument and then connected to the device under test to make a measurement.
Why are digital multimeters used?
A DMM is primarily used to verify one of the three factors of Ohm’s Law voltage (volts), current (amps) and resistance (ohms). This simple equation, expressed below, is commonly used by electrical engineers during diagnostic testing.
V = I x R
V = voltage
I = current
R = resistance
Engineers in the lab and in the field also use digital multimeters to verify the state of a system or circuit for safety purposes. For instance, voltages in excess of 42V or currents in excess of 10 mA can provide painful shocks, and in some cases, be lethal. Resistances are also rated for certain powers (watts) and can get hot when driving higher currents and voltages. Digital multimeters essentially help engineers verify that a device under test is safe to work on.
Types of digital multimeters
General purpose digital multimeter
|General Purpose Multimeter||Used By||Used To||Form Factor||Overview|
|Beginners and Hobbyists||Troubleshooting simple circuits and get a general idea of what is and isn't working.||Handheld||They don't provide a high degree of accuracy but readings are fool proof.|
Often used by hobbyists, these DMMs measure voltage, resistance, continuity and current to troubleshoot simple circuits. They don’t provide a high degree of accuracy—just a general idea of what’s working. Simplicity is key and readings are fool proof.
|Handheld Digital Multimeter||Used By||Used To||Form Factor||Overview|
|Electricians, electrical contractors and HVAC specialists||Make measurements and troubleshoot potentially hazardous system in the field.||Handheld||Handheld DMMs should be used when mobility is required.|
Also known as digital voltmeters, handheld digital multimeters are used by electricians, electrical contractors and HVAC specialists to make measurements and troubleshoot potentially hazardous systems in the field. Handheld DMMs should be used when mobility is required.
|Advanced Digital Multimeter||Used By||Used To||Form Factor||Overview|
|Electrical and electronic engineers||Perform more advanced measurements and gain confidence in their designs.||Bench Top||These DMMs are extremely precise and have a variety of advanced functionality|
Also known as bench DMMs or commercial DMMs, these instruments are used by electrical and electronic engineers to perform more advanced measurements and gain confidence in their designs. These instruments are extremely precise and have a variety of advanced functionality, including the ability to program automation, slow or speed up measurements to observe low-level or transient signal behavior, and interface with other instruments.
|Compact Digital Multimeter||Used By||Used To||Form Factor||Overview|
|Electrical and electronic engineers||Perform more advanced measurements and gain confidence in their designs.||Rack Mounted||Used when precise measurements are needed, but space is limited.|
These multi-channel multimeters are used in manufacturing when precise measurements are needed, but equipment space is limited. They embed cards with switches and mux to "squeeze" tens or even hundreds of channels into a single mainframe.
Digital multimeter vs. oscilloscope
A digital multimeter allows you to read the voltage at any one moment in time, but oscilloscopes show how the voltage changes over time by graphically displaying a waveform. Oscilloscopes are often used over digital multimeters when troubleshooting more complex circuits.
|Digital Multimeter||Used to:||Circuit type:|
|Read the voltage at any one moment in time.||Simple Circuits|
|Oscilloscope||Used to:||Circuit type:|
|Measure how the voltage changes over time.||Complex Circuits|
How to Choose a Digital Multimeter
When it comes to choosing the right digital multimeter for your application, there are a number of considerations, starting with where you will be using it. You’ll also want to look at accuracy, speed and the number of channels needed to ensure the instrument will meet the demands of your job.
How to find the best digital multimeter for your needs
- Don’t break the bank: DMM6500, 2100 Series, 2110 Series
- The most precise reading: DMM7510, 2002 Performance DMM
- The need for speed: DMM6500, DAQ6510, DMM7510
- Give me more channels: DAQ6510, DAQ2750, 3700A
- I want it all: DMM7512
How to use a digital multimeter
A digital multimeter is very easy to set up and use to run tests in the lab. Simply follow the six steps below to set up your digital multimeter and start measuring a device under test (DUT).
Note: The steps above cover the basics of how to use a digital multimeter, but engineers should always consult the model-specific instruction manual before operating a digital multimeter to ensure practices are safe and measurements are accurate.
Digital multimeter resources
Ready to take your DMM knowledge to the next level? Learn more about digital multimeters and how to use them in the Tektronix Learning Center, where you can find these and many other resources:
- Digital multimeter selector guide
- Temple University IDEAS Hub Education Case Study
- Top Five Digital Multimeter User Questions (and Our Answers)
- Getting Back to the Basics of Electrical Measurements